Palestinian officials say Prime Minister Mahmoud Abbas has broken off contacts with the militant groups Hamas and Islamic Jihad after they claimed responsibility for Tuesday's suicide bombing that killed 20 people in Jerusalem.

Mr. Abbas was holding talks with the militants when the attacker blew up a crowded bus. Officials from Hamas and Islamic Jihad say the blast does not mean an end to the cease-fire announced by militant groups in late June.

Meanwhile, Israeli radio reports Israel is planning to cordon off the West Bank and Gaza Strip in response to the attack. Israel also froze all contacts with the Palestinian Authority and called off the expected security handover of two Palestinian towns, Qalqilyah and Jericho.

The White House condemned the attack as a vicious act and called on the Palestinian Authority to dismantle terrorist organizations. Mr. Abbas also denounced the blast.

Report from JerusalemVOA Correspondent Ross Dunn has more on the prime minister's reaction in this report:

The Palestinian prime minister, Mahmoud Abbas, has condemned a suicide bombing in Jerusalem on Tuesday that has killed at least 20 people on a bus and wounded more than 100 people. The militant Palestinian Islamic group Hamas has claimed responsibility for the explosion, but Mr. Abbas urged Israel not to launch any military retaliation, saying this could further harm peace efforts.

Mr. Abbas described the bombing as a "horrible act" and condemned it.

He expressed his sorrow to the families of the victims of the attack, many of whom were Orthodox Jews, traveling home on the bus after prayers at the Western Wall, a Jewish holy site in Jerusalem's Old City.

Mr. Abbas said the bombing did not serve the interests of the Palestinian people and he had instructed his security minister, Mohammad Dahlan, to begin an immediate investigation.

He had been meeting with Palestinian militant groups in Gaza when the explosion occurred. Mr. Abbas had been urging them to hold to a three month unilateral truce they had declared in June.

Mr. Abbas said he hoped Israel would act "wisely" and refrain from launching any military response, saying that this, in his words, "will not be in the interest of the peace process."

Following the blast, Israel announced it was suspending the planned handover of four West Bank cities to Palestinian security control, while it evaluated the security situation. Israel also froze all contacts with the Palestinian Authority.

Hamas, a group that frequently carries out suicide bombings, said it was responsible for the bombing.

A videotape released by Hamas in the West Bank city of Hebron showed a Palestinian man who identified himself as a Hamas activist. He said he would carry out the suicide bombing to avenge Israel's killing of one the group's members.

Earlier, Islamic Jihad, another group that carries out suicide bombings, also claimed responsibility for the attack.

Israeli officials said they were investigating the possibility that Hamas and Islamic Jihad had been involved in a joint operation.